The term "polyphenylene ether resin" includes a family of polymers well known to those skilled in the art, and they are made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. Nos. 3,306,974 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,257,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes for preparing polyphenylene ether resins, including graft copolymers of polyphenylene ethers with styrene type compounds, are found in Fox, U.S. Pat. No. 3,356,761; Sumitomo, U.K. Pat. No. 1,291,609; Bussink et al, U.S. Pat. No. 3,337,499; Blanchard et al, U.S. Pat. No. 3,219,626; Laakso et al, U.S. Pat. No. 3,342,892; Borman, U.S. Pat. No. 3,344,166; Hori et al, U.S. Pat. No. 3,384,619; Faurote et al, U.S. Pat. No. 3,440,217; and disclosures relating to metal based catalysts which do not include amines, are known from patents such as Wieden et al, U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio et al, U.S. Pat. No. 3,573,257 (metal-alcoholate or -phenolate); Kobayashi et al, U.S. Pat. No. 3,455,880 (cobalt chelates); and the like. In the Stamatoff patents, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, an acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead dioxide, silver oxide, etc., are described in Price et al, U.S. Pat. No. 3,382,212. Cizek, U.S. Pat. No. 3,383,435 discloses polyphenylene ether styrene resin compositions. Katchman, U.S. Pat. No. 3,663,661 also discloses polyphenylene ether resin compositions. All of the above-mentioned disclosures are incorporated herein by reference.
Compositions of polyphenylene ethers have been known to exhibit inferior physical properties after exposure to thermal stress for prolonged periods. Also ultraviolet light tends to degrade polyphenylene ether resins. This has resulted in a need for stabilizers that prevent embrittlement of these compositions. Applicant has now discovered that the use of a minor amount of an N-alkanoyl-p-aminophenol in polyphenylene ether compositions will produce a composition that has greatly enhanced resistance to thermal degradation and degradation induced by ultraviolet light.
Accordingly, it is a primary object of this invention to provide polyphenylene ether compositions that have improved resistance to thermal aging.
It is also an object of this invention to provide a new method for imparting thermal stability to a polyphenylene ether resin composition.
It is also an object of this invention to provide polyphenylene ether compositions that are stable to ultraviolet light.